How Should Different Types of Plastics Be Recycled?
Plastic recycling plays a vital role in reducing pollution, conserving resources, and promoting a circular economy. Below are six common recycled plastic processing methods, including LDPE, PP, PET, ABS, PC, and PVC. Each has its own recycling process depending on material characteristics and end-use applications.
1. LDPE
LDPE (Low-Density Polyethylene), also known as high-pressure polyethylene, is commonly used for plastic packaging films such as woven bag liners, food packaging films, daily product wraps, and agricultural greenhouse films.
Before recycling, LDPE films should be sorted by color and must not be mixed with HDPE, PP, OPP, or PVC films to ensure quality.
LDPE recycling process:
1. Crushing and Washing
The LDPE films are crushed with water to remove impurities. Clean, high-quality LDPE can be reused for film blowing without adding virgin material. To improve cleanliness, crushed flakes are further rinsed and agitated in a water tank.
2. Drying
The washed materials are dehydrated using a centrifugal dryer and then sun-dried when possible to save energy. It’s essential to avoid secondary contamination during drying.
3. Pelletizing
The clean flakes are melted and extruded into pellets using a specialized plastic extruder.
Through 60–80 mesh filters, pellets can be reused for film blowing.
Through 40–60 mesh filters, pellets are suitable for injection molding.
Generally, transparent or light-colored LDPE is used for high-quality films, while darker or mixed-color materials are made into garbage bags or injection-molded products.
4. Cutting and Packaging
The extruded strands are cooled and cut into pellets. Separate packaging for film-grade and injection-grade pellets prevents confusion. Film-grade pellets should be packed with inner liners to avoid contamination.
2. PP
PP (Polypropylene) is widely used in household goods such as plastic basins, buckets, chairs, stools, woven bags, packing straps, and other daily-use items.LDPE recycling process:
PP recycling process:
1. Sorting
Separate materials by color to enhance final product quality and market value.
2. Crushing and Drying
Wash and crush the PP products with water, then dehydrate using a centrifugal dryer and sun-dry completely.
3. Mixing and Pelletizing
Mix the dried material in a mixer with a small amount of color masterbatch and additives, then feed it into a PP pelletizing extruder.
The extrusion temperature must be properly controlled to avoid brittleness.
4. Water-Cooling and Cutting
Cool the extruded strands in water and cut into 3×4 mm uniform pellets for a smooth and standard appearance.
3. PET
PET (Polyethylene Terephthalate) is a semi-crystalline thermoplastic polymer widely used in beverage bottles, food packaging, and cosmetic containers due to its light weight, strength, and low energy consumption.
PET recycling process:
1. Sorting and Label Removal
Separate PET bottles by color and remove labels (often made of OPP or PVC shrink film) to prevent contamination.
2. Crushing and Pre-Washing
Crush bottles with water to remove dust and residues.
3. Hot Washing
Wash the flakes with hot water and caustic soda to remove oil and glue residues.
4. Rinsing and Drying
Thoroughly rinse with clean water, then dehydrate and dry in a vacuum oven.
5. Reprocessing
The dried PET flakes can be further processed into fibers, film, or other recycled plastic products through extrusion and stretching.
4. ABS
ABS (Acrylonitrile Butadiene Styrene) mainly comes from discarded electrical appliance casings (computers, TVs, instrument panels), automotive interior parts, and other household products.
ABS recycling process:
1. Sorting
Separate materials by color and surface treatment (painted, plated, or plain).
2. Chemical Treatment
Use specific chemical solutions for paint or plating removal. Operators should wear protective equipment and handle with care.
3. Washing and Drying
Clean and dry the treated materials. Add colorants or additives as needed to improve quality.
4. Pelletizing
Use an ABS extrusion granulator with an appropriate filter mesh according to product requirements.
5. PC
PC (Polycarbonate) is a high-performance engineering plastic used in automotive lighting parts, optical discs, telecommunication devices, and molds.
PC recycling process:
1. Sorting and Selection
Classify PC materials by transparency and color (clear, blue, red, green, black, etc.). Distinguish between pure and modified materials, as well as coated items like CDs or lampshades.
2. Cleaning and De-Coating
Remove coatings or films using chemical solutions similar to the ABS process. Then rinse and dry the material.
3. Color Adjustment
Depending on product needs, add color masterbatch or stabilizers. Yellowish PC can be modified to off-white, and clear PC can remain transparent.
4. Extrusion and Pelletizing
Extrude and cut into pellets using a specialized PC extruder. Because PC is prone to aging, the recycling temperature and processing time should be carefully controlled to maintain quality.
6. PVC
PVC (Polyvinyl Chloride) hard materials are mainly derived from building materials, window and door frames, pipes, chemical valves, and decorative panels.
PVC recycling process:
1. Sorting
Classify by color (white, gray, or black). Avoid mixing with other plastics such as PP or PE.
2. Crushing and Washing
Crush and wash materials with water to remove dirt. Dry thoroughly to prevent contamination.
3. Mixing and Additives
Mix the clean PVC flakes with additives or color masterbatch as needed.
4. Extrusion and Pelletizing
Use a dedicated PVC extrusion granulator for pelletizing, followed by cooling, packaging, and labeling.
Conclusion
Recycling different types of plastics—such as LDPE, PP, PET, ABS, PC, and PVC—not only reduces plastic waste but also conserves raw materials and energy. With advances in plastic recycling technology, modern processes are becoming more efficient, clean, and sustainable, supporting global efforts toward an eco-friendly circular economy.
